1. Field of Invention
The present invention relates to electro-optical devices and electronic equipment. Particularly, the invention relates to electro-optical devices which use pole-like spacers to maintain a predetermined gap between the two pieces of substrates and of electronic equipment provided with such electro-optical devices.
2. Description of Related Art
A related art electro-optical device, such as a liquid crystal device, can be constituted by sealing liquid crystals, which is an exemplary electro-optical substance, between two substrates on which are fabricated electrodes, wirings, elements, etc. In the electro-optical device of this kind, a so-called spacer is usually provided to maintain the gap between the two pieces of substrates, i.e., to maintain the thickness of the layer of liquid crystals (hereinafter “cell gap”) constant (e.g., about 3 to 5 μm) over the whole surfaces of the substrates. The cell gap must be maintained constant. Otherwise, display characteristics are affected, such as transmission factor of light, contrast ratio, response speed, etc., and in bad cases, there may occur shading in the display.
More concretely, a spacer having a tiny spherical shape can be used, for instance. In the case of a direct viewing type (large type) liquid crystal display device, such as a liquid crystal TV or monitor, a number of such very small nearly spherical spacers are used which are homogeneously sprinkled in the liquid crystals between the two pieces of substrates. On the other hand, in the case of a small liquid crystal display device to display on an enlarged scale, for example, a light bulb of a projector, a spacer is used that is mixed in a sealing material that is used to adhere the two pieces of substrates together.
Another type of the spacer having a so-called pole shape (hereinafter “pole-like spacer”) is also used. This is a spacer used in a form in which pole-like members that are made of a suitable organic material are erected on the substrate maintaining a suitable gap, and works to support two pieces of the substrates with a yield strength in the axial direction of the poles to maintain the cell gap therebetween constant. The “suitable gap” is provided such that, for example, there is a pole-like spacer in every several pixels to every several tens of pixels. Even when such pole-like spacers are used, it is generally accepted to use them in combination with the above nearly spherical spacer that is mixed in the sealing material (hereinafter, the spacer in the sealing material is particularly referred to as “gap material”). This makes it possible to more favorably satisfy the requirement of maintaining the cell gap constant over the whole surfaces of the substrates.
In maintaining the gap between the substrates “constant”, the accuracy differs depending upon differences in the “twisted angle” of liquid crystal molecules, constituting the layer of liquid crystals, between the two pieces of substrates. In the case of the TN (twisted nematic) having the twisted angle of, for example, 90°, the accuracy of ±0.1 μm or less is required. In the case of the STN (super-twisted nematic) having the twisted angle of, for example, 260°, the accuracy of ±0.3 μm or less is required.